The 45-degree diagonal produces an image that is correctly oriented, meaning that the image is vertical and correct from left to right (ie, a correct image, not inverted). This is a great diagonal for daytime terrestrial use with any Refractor Telescope. It can also be used for nighttime astronomy applications, especially when you want to match the orientation of the star field with “correct” star charts and maps The clear opening is 19.5mm. The prism housing is made of metal and with high grade ABS and the end barrels are made of precision machined aluminum. The 1.25″ nozzle is threaded to accept standard 1.25″ astronomy filters.

This diagonal can only be used with refracting telescopes and some catadioptric telescopes. It is not used for Newtonian / Dobsonian telescopes or other variants of Newtonian telescopes.